New Zealand Journal of Marine and Freshwater Research abstracts

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Reproductive output of male seahorses, Hippocampus abdominalis, from Wellington Harbour, New Zealand: implications for conservation

Chris M. C. Woods

National Institute of Water and Atmospheric
Research Limited
P.O. Box 8602, Riccarton
Christchurch, New Zealand
email: c.woods@niwa.co.nz

Abstract  This investigation examines aspects of reproductive output in brooding wild male seahorses, Hippocampus abdominalis, from Wellington Harbour, New Zealand. Previously undocumented, such information is crucial to the management and protection of this species in relation to the CITES Appendix II-listing of all seahorse species. Brooding males (n = 46) were captured and kept captive until the release of their juveniles, whereupon the number of juveniles was counted and sampled for standard length (SL) and dry weight (DW). SL (mean ±1SE) of brooding males was 18.1 ± 0.6 cm and wet weight (WW) 17.6 ± 1.6 g. Number (mean ±1SE) of juveniles released per brood was 271.2 ± 27. The number of juveniles produced was positively correlated with parent SL, WW, and brood pouch volume. Brood pouch volume was positively correlated with male SL. SL (mean ±1SE) of juveniles released was 16.7 ± 0.2 mm and DW 1.2 ± 0.1 mg. Mean SL and DW of juveniles were not correlated with the number of juveniles per brood, parent male SL or parent male pouch volume. The percentage of pouch contents which were non-viable (i.e., premature or non-viable eggs) upon juvenile release was low (1.1 ± 0.2%; mean ±1SE of the total pouch contents). Based on findings in this study it is suggested that the CITES 10 cm minimum height restriction, which can be used in lieu of non-detriment findings to allow sustainable exploitation of seahorses, is not suitable for H. abdominalis from Wellington Harbour as it would appear to only protect small males that produce low numbers of juveniles.

Keywords  Syngnathidae; CITES; Hippocampus abdominalis; juveniles; pouch volume; brood size; minimum size limit

M04125; Online publication date 17 June 2005 Received 7 July 2004; accepted 18 January 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39: 881-888
0028-8330/05/3904-0881 © The Royal Society of New Zealand 2005

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